Flight and Fuel Management
The pilot conducted a flight lasting about four hours. He flew for one-hour periods alternating between the right and left fuel tanks, first on the right tank, then the left tank, and then back to the right tank. He then reselected the left tank and observed that the right tank indicated empty. Approximately 25 minutes later, the engine lost power. The pilot initiated a forced landing onto a road. During the landing, the airplane struck a sign and veered off the road into rocks, causing the nose gear to collapse.
During the flight, the pilot maintained an altitude of 1,000 feet for the initial portion, then climbed to 6,500 feet, and subsequently descended to 4,500 feet for the remainder of the flight. He cruised at 2,500 rpm throughout and leaned the mixture to 100° rich of peak exhaust gas temperature (EGT).
Engine Performance Calculations
The performance section of the Pilot's Operating Handbook (POH) stated that cruise power settings and cruise fuel flow should be selected using the Lycoming Operator's Manual (LOM). This manual was not present in the airplane, and the pilot did not reference one during his preflight planning. He had never used this manual during his training or checkout in this type of airplane.
The operating conditions section of the LOM specified that performance cruise at 75 percent rated power required 2,450 rpm, 135 horsepower, and a fuel consumption of 10.5 gallons per hour (gph). Above 75 percent power, it stated to maintain the mixture control in the full rich position.
Lycoming engineers utilized the sea level and altitude performance chart at standard temperatures to determine the power generated under the conditions reported by the pilot. For the portion of the flight at 1,000 feet, the airplane was generating 165 horsepower and consuming fuel at a rate of 13.49 gph. At 6,500 feet, 134 horsepower was generated with a fuel consumption of 10.95 gph. At 4,500 feet, 144 horsepower was generated with a fuel consumption of 11.77 gph.
Post-Accident Inspection
After the accident, the aircraft was examined. The retriever drained 18 ounces of blue fuel from the wing fuel tanks and 3 ounces from the sediment bowl. An inspection revealed that the fuel vents were clear, fuel flowed through the system without leaks, and the spark plugs were clean.